How cold must it be to see your breath?

[douglips]

@Shoeless

Maybe I’m oversimplifying or not taking other factors into account, but to me it seems that the obvious answer is “whatever the dewpoint is”. If not, why not?

If the temperature of the air is equal to the dewpoint, it’s foggy.

So, sure, if the air temperature is less than the dewpoint of your breath, that’s how you get foggy breath. But it has little to do with the dewpoint of the air around you.